Method and apparatus for controlling erosion in a downhole tool

ABSTRACT

A drill string is comprised of a tubular element and an elastomeric element. The tubular element has an interior surface and a longitudinal axis. The elastomeric element is positioned on the interior surface of the tubular element, and includes one or more ribs extending from the interior surface of the tubular element and arranged in a configuration that diverges from the longitudinal axis of the tubular element. The ribs form an opening within the tubular element having a diameter of a preselected size substantially similar to a diameter of a tool to be positioned therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND

The disclosed subject matter relates generally to a method and apparatus for protecting down-hole instruments in a well, and, more particularly, to one or more elements positioned in an annulus formed between an interior surface of a well collar and the down-hole instrument to reduce or prevent contact between the down-hole instrument and the well collar without adversely affecting the control of fluids in the annulus.

Drilling, completing, and producing hydrocarbon and other wells are generally complicated and expensive operations. Accordingly, monitoring the condition of the well and performing routine maintenance on the well are useful in maintaining its proper health so as to extend the useful life of, and production from, the well.

Such monitoring and maintenance of the well is generally provided by instruments that are inserted into the well drill pipe or tubing string and lowered into the well until the instrument reaches a region of the well that is to be examined or otherwise tested. These instruments may take on any of a variety of forms, but many are particularly sensitive to shock and vibration that may be caused by contact between the instrument and the interior surface of the well, particularly in modern well bores produced by directional drilling. For example, as shown in FIG. 1, a drill string 110 is shown in a well 120 that has been produced by directional drilling such that the well 120 curves substantially away from a vertical axis to produce a curved region 130. As the instrument 140 is lowered into the well it is likely to come into contact with the interior surface of the drill string 110, particularly in the curved region 130.

To reduce the likelihood and/or severity of contact between the instrument 140 and the drill string 110, it has been proposed to place elastomeric elements within the drill string such that the instrument 140 contacts the softer elastomeric elements, rather than hard surface of the drill string 110. Cushioning provided by the elastomeric elements is useful in reducing or preventing damage caused by contact between the instrument 140 and the drill string 110. However, these elastomeric elements are positioned within the annulus between the instrument 140 and the drill string 110 where mud or drilling fluid is typically circulating. The presence of these elastomeric elements in the annulus restricts the flow of drilling fluid and produces turbulent flow. Those skilled in the art will appreciate that turbulent flow of the drilling fluid can produce substantial erosion of the surface of the instrument 140. That is, over time, the turbulent drilling fluid flow wears away and damages the housing 150 of the instrument 140, causing variations in the accuracy of the instrument 140, and/or ultimately causing a failure of the instrument housing 150. Such a failure of the housing 150 may expose sensitive and expensive electronic circuitry and sensors contained therein to be damaged or entirely destroyed. Further, such turbulent flow can also erode the surface of the drill string 110 and its related components, which can lead to collar washouts, valve failures, and pressure housing leaks, which can result in down-hole failures.

BRIEF SUMMARY

The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an exhaustive overview of the disclosed subject matter. It is not intended to identify key or critical elements of the disclosed subject matter or to delineate the scope of the disclosed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

One aspect of the disclosed subject matter is seen in an apparatus that is comprised of a tubular element having a plurality of rib elements affixed to an interior surface of the tubular element. At least a portion of the rib elements are coupled to the interior surface of the tubular element and extend longitudinally along at least a portion of the interior surface of the tubular element in a helical pattern. The rib elements extend radially from the interior surface of the tubular element to form a longitudinal opening that has a diameter of a size related to a diameter of a down-hole instrument to be inserted therein.

Another aspect of the disclosed subject matter is seen in an alternative embodiment that is comprised of a tubular element having an elastomeric feature affixed to an interior surface of the tubular element and substantially covering the interior surface of the tubular element. The elastomeric element may have a plurality of rib elements extending from the interior surface of the tubular element. At least a portion of the rib elements extend longitudinally along at least a portion of the interior surface of the tubular element in a helical pattern. The rib elements extend radially from the interior surface of the tubular element to form a longitudinal opening that has a diameter of a size related to a diameter of a down-hole instrument to be inserted therein.

Another aspect of the disclosed subject matter is seen in a method for forming an elastomeric element on an interior surface of drill string. The method comprises positioning a mandrel within the drill string to form a void between the interior surface of the drill string and the mandrel. The method further comprises injecting an elastomeric material into the void, and removing the mandrel from the drill string.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosed subject matter will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

FIG. 1 is a stylistic side view of a well being examined or otherwise tested by a down-hole instrument;

FIG. 2 is a cross-sectional side view of a down-hole instrument;

FIG. 3 is a cross sectional end view of a first embodiment of a drill string employing an elastomeric element having a plurality of ribs positioned to form an opening sufficient to accept the down-hole instrument therein;

FIG. 4 is a cross sectional end view of an alternative embodiment of a drill string employing an elastomeric element having a plurality of ribs positioned to form an opening sufficient to accept the down-hole instrument therein;

FIG. 5 is a cross sectional end view of the embodiment of the drill string shown in FIG. 4 with the down-hole instrument having been removed;

FIG. 6 shows a stylistic view of a down-hole instrument attached to a wireline to facilitate being lowered into a drill string in a well;

FIG. 7 shows a cross-sectional side view of a down-hole instrument inserted into a drill string having elastomeric ribs located therein;

FIG. 8 shows a cross sectional side view of a down-hole instrument inserted into a drill string having an alternative embodiment that includes a plurality of longitudinally spaced apart elastomeric elements coupled to the down-hole instrument;

FIGS. 9A and 9B show plan views of an interior surface of drill string that has been unrolled to form a flat surface for ease of illustration, wherein the interior surface of the drill string includes elastomeric elements affixed thereto in a helical pattern; and

FIG. 10 is a longitudinal cross sectional view of a drill string with a mandrel positioned therein to form a void in which an elastomeric element may be formed.

While the disclosed subject matter is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the disclosed subject matter to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosed subject matter as defined by the appended claims.

DETAILED DESCRIPTION

One or more specific embodiments of the disclosed subject matter will be described below. It is specifically intended that the disclosed subject matter not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but may nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. Nothing in this application is considered critical or essential to the disclosed subject matter unless explicitly indicated as being “critical” or “essential.”

The disclosed subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the disclosed subject matter with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the disclosed subject matter. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

Referring now to the drawings wherein like reference numbers correspond to similar components throughout the several views, the disclosed subject matter shall be described in the context of being deployed in a well, particularly during operations associated with actually drilling the well.

Turning first to FIG. 2, a cross-sectional side view of a down-hole instrument 140 is shown. The instrument 140 includes a housing 150, which may be formed of any of a variety of materials suitable for withstanding a hostile environment typically found in, for example, a hydrocarbon well, including but not limited to metals, such as beryllium copper. In one embodiment, the housing is substantially tubular in configuration, having a substantially circular sectional configuration. The length and diameter of the housing 150 may vary substantially, according to the instrumentality intended to be employed therein. For example, the interior of the housing 150 may include a variety of sensing, measuring, computing, and storing devices that are configured to make measurements associated with the geology of the well, the operating characteristics of a drill, the location of the instrument 140, etc. These devices may include magnetometers 205, accelerometers 210, and the like. The housing may also include power supplies 215, computing devices 220, memory 225, and telemetry units 230.

Those skilled in the art will appreciate that the devices contained within the housing 150 may be electronic in nature, and thus, may be destroyed or rendered ineffectual if exposed to drilling fluids. Furthermore, some elements contained within these protective housings may incorporate downhole energy storage or power generating systems which when exposed to drilling fluids, water, oil or any other fluids may react and cause damage to the devices or other components in the well. Accordingly, the housing 150 includes conventional sealing means, such as gaskets, O-rings, and the like to isolate the devices contained within the housing 150 and prevent exposure to drilling fluids. Likewise, the devices contained in the housing 150 may also be sensitive to vibration, shock, etc., and may be destroyed or rendered ineffectual if subjected to forces of substantial magnitude and/or duration. Accordingly, elastomeric elements are employed to reduce the likelihood of, or effect of, instances of vibration and shock being applied to the housing 150.

FIG. 3 is a cross sectional end view of a first embodiment of a drill string 110 employing an elastomeric element 300 disposed within the drill string 110 and in contact with the interior surface of the drill string 110. In one embodiment, the elastomeric element 300 covers substantially all of the interior surface of the drill string 110 and serves to protect the interior surface of the drill string 110 from damage caused by exposure to drilling fluids or other chemicals, impurities, and the like commonly found in drilling fluids during a drilling operation. In the illustrated embodiment, the elastomeric element 300 may include a plurality of ribs 305 affixed to an interior surface 300 of the drill string 110 and oriented to form an opening of a size sufficient to accept the instrument 140 therein. The elastomeric element 300 may be formed of any of a variety of materials, including, but not limited to, rubber, synthetic rubber, synthetic rubber copolymer, or the like, such as Nitrile rubber, Nitrile butadiene rubber, acrylonitrile and butadiene, and the like.

The drill string 110 is substantially tubular in configuration and has an interior diameter substantially larger than the outer diameter of the housing 150. The ribs 305 may take on any of a variety of cross sectional configurations, including but not limited to configurations having curvilinear surfaces or linear surfaces, such as, but not limited to half circles, triangles, squares, rectangles, trapezoids, other complex polygons, or the like. The height 310 of the ribs 305 may be selected to form an interior passage having a diameter substantially similar to the external diameter of the housing 150, allowing the housing 150 to pass longitudinally through the drill string 110 while limiting radial movement of the housing 150. The thickness of the elastomeric element 300 in the region between the ribs 305, which covers the tubular inside diameter between the ribs 305 can also be varied to optimize the hydraulic flow performance. Those skilled in the art will appreciate that drilling fluids may flow longitudinally through regions 315 between each of the ribs 305.

It is anticipated that the drill string 110 may be subject to forces that will cause the drill string 110 to bend or flex along its longitudinal axis. Accordingly, in some embodiments it may be useful to reduce the height of the ribs 305 to increase the diameter of the interior passage formed between the ribs 305 so that the housing 150 may readily pass therethrough even in instances of substantial bending or flexing of the drill string 110 along its longitudinal axis. Those skilled in the art will appreciate that the system of ribs 305 may be engineered and optimized to allow for the response of the elastomeric material when exposed to various drilling fluids and various fluid chemistries.

FIG. 4 is a cross sectional end view of an alternative embodiment of a drill string 110 employing an elastomeric element 400 with a plurality of ribs 405 positioned to form an opening sufficient to accept the instrument 140 therein. In the illustrated embodiment, three ribs 405 are symmetrically positioned about the interior surface of the drill string 110. Those skilled in the art will appreciate that drilling fluids may flow longitudinally through the regions 410 between each of the ribs 405. The ribs 405 have a curvilinear cross sectional configuration that rises to a peak 410 that may come into substantial contact with the housing 150, particularly in instances where the drill string 110 is experiencing bending or flexing along its longitudinal axis. Further, the regions of the elastomeric element 400 between the ribs 405 may be relatively thin to maintain a substantial longitudinal passage for drilling fluids to flow therein, but still sufficiently thick to protect the interior surface of the drill string 110 from the drilling fluids.

FIG. 5 is a cross sectional end view of the drill string 110 of FIG. 4 with the instrument 140 removed therefrom.

FIG. 6 shows a stylistic view of a drilling rig 600 configured to lower the down-hole instrument 140 via, for example a wireline to facilitate the instrument 140 being lowered into a drill string 110 in a well. The drilling rig 600 and wireline may be of a conventional configuration and arranged to raise and lower the instrument 140 within the drill string 110, as needed. FIG. 7 shows a cross-sectional side view of a down-hole instrument 140 inserted into a portion of a drill string 110 having an elastomeric element 700 with ribs 705 formed therein. The ribs 705 extend both radially and longitudinally from the interior surface of the drill string 110 to form an opening having a diameter substantially similar to the outer diameter of the instrument 140 such that contact between the instrument 140 and the interior surface of the drill string 110 is avoided or at least reduced, especially when the drill string 110 is experiencing forces that bend or flex the drill string 110 along its longitudinal axis. In some embodiments, it may be useful to form each of the elastomeric elements 705 as a single unit that extends substantially the entire length of the drill string 110. Alternatively, in some embodiments, it may be useful for the elastomeric elements 705 to be formed from separate elements that are longitudinally spaced apart. For example, FIG. 8 shows a cross sectional side view of a down-hole instrument 140 inserted into a drill string 110 that includes a plurality of longitudinally spaced apart elastomeric elements 805 coupled to the interior surface of the drill string 110.

FIGS. 9A and 9B show plan views of an interior surface of drill string 110 that has been diagrammatically unrolled to form a flat surface for ease of illustration. The interior surface 900 of the drill string 110 includes an elastomeric element 900 that includes ribs 905 affixed thereto in a pattern that may diverge from the longitudinal axis of the drill string 110, such as a helical or corkscrew pattern. In one embodiment, such as is illustrated in FIG. 9A, the elastomeric elements 905 have a twist of about 1 revolution within a standard drill string length of about 9 feet. In other embodiments, it may be useful for the elastomeric elements 905 to have greater or fewer revolutions within the same distance. For example, FIG. 9B illustrates an embodiment in which the elastomeric elements twist at a rate of about 2 revolutions within a standard drill string length of about 9 feet. Those skilled in the art will appreciate that the number of elastomeric elements may vary as desired. For example, in some embodiments, such as is illustrated in FIG. 9B, a single elastomeric element 905 may be employed with a higher revolutionary, whereas in other embodiments, such as is illustrated in FIG. 9A it may be useful to have multiple elastomeric elements, such as 3, with a lower revolutionary rate.

Higher revolutionary rates may be useful in applications where lower flow rates may be used with respect to the drilling fluids. On the other hand, where higher flow rates are desirable, it may be useful to use a lower revolutionary rate with respect to the helical pattern of the elastomeric elements 905. In either embodiment, those skilled in the art will appreciate that drilling fluid will flow freely in the voids formed between the elastomeric elements 905 and the instrument 140.

It is anticipated that the helical embodiment described herein will result in controlled, non-turbulent flow of the drilling fluid. Those skilled in the art will appreciate that turbulent flow creates heat and may be abrasive, creating an undesirable wearing on the surface of the housing 150 of the instrument 140. Over time, this abrasive wearing of the housing may result in failure of the housing 150 and resultant damage to the devices contained therein.

In one embodiment, the elastomeric elements shown in the preceding figures, including the ribs and webs extending therebetween, may be created and attached to the inside diameter of the drill string 110 by a high pressure injection molding process. As shown in the longitudinal cross sectional diagram of FIG. 10, a mandrel 1000 may be inserted into the drill string 110 and be of a sufficient size and cross sectional shape to leave a void 1005 between the drill string 110 and the mandrel 1000. The shape of the void 1005 may be controlled by adjusting the configuration of the mandrel 1000. In the embodiment illustrated in FIG. 10, the mandrel 1000 has been configured produce the void 1005 having a shape substantially similar to the shape of the elastomeric elements 400, 500 shown in FIGS. 4 and 5.

An elastomer may be injected into the void 1005 at a controlled temperature. The mandrel 1000 may be heated to about the injection temperature of the elastomer. Likewise, the drill string 110 may also be heated to about the injection temperature of the elastomer.

The mandrel 1000 may be mechanically supported during the injection process to maintain the shape of the void 1005. The mandrel 1000 and its mechanical supports (not shown) may be removed at specific times during the injection and curing process. In one embodiment, it may be useful to include one or more supports 1010 spaced along the longitudinal length of the drill string 110. In this manner, sagging or bending of the mandrel 1000 along its longitudinal length may be reduced or substantially eliminated. Those skilled in the art will appreciate that the mandrel 1000 and the supports 1010 may be removed at a desired time after curing of the elastomeric element in the void 1005 has achieved a desired status. In the embodiment illustrated in FIG. 10, the mandrel 1000 is shown to have a substantially corkscrew or helical configuration, which produces a void 1005 that will result in an elastomeric elements similar in shape and configuration to that shown in FIGS. 9A and 9B. Those skilled in the art will appreciate that other shapes and configurations of the elastomeric element may be achieved by varying the configuration and positioning of the mandrel 1000 within the drill string 110.

Further, in some embodiments it may be useful to prepare the inner surface of the drill string 110 so as to enhance adhesion between the elastomer and the inner surface of the drill string 110. For example, the inner surface of the drill string 110 may be machined or otherwise roughened to provide a desired rugosity that will more readily and effectively bond with the elastomer.

The particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below. 

We claim:
 1. A drill string, comprising: a tubular element having an interior surface and a longitudinal axis; and at least one elastomeric element positioned on the interior surface of the tubular element, the elastomeric element having one or more ribs extending from the interior surface of the tubular element and arranged in a configuration that diverges from the longitudinal axis of the tubular element.
 2. A drill string, as set forth in claim 1, wherein the one or more ribs form an opening within the tubular element having a diameter of a preselected size.
 3. A drill string, as set forth in claim 2, wherein the opening diameter formed by the one or more ribs is substantially similar to a diameter of a tool to be positioned therein.
 4. A drill string, as set forth in claim 1, wherein the one or more ribs are arranged in a helical configuration.
 5. A drill string, as set forth in claim 1, wherein the one or more ribs are arranged in a corkscrew configuration.
 6. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from a synthetic rubber.
 7. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from a synthetic rubber copolymer.
 8. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from a Nitrile rubber.
 9. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from a, Nitrile butadiene rubber.
 10. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from acrylonitrile.
 11. A drill string, as set forth in claim 1, wherein the elastomeric element is formed from butadiene.
 12. A drill string, as set forth in claim 1, wherein the elastomeric element covers substantially the entire inner surface of the drill string.
 13. A method for forming an elastomeric element on an interior surface of drill string, comprising: positioning a mandrel within the drill string to form a void between the interior surface of the drill string and the mandrel; injecting an elastomeric material into the void; and removing the mandrel from the drill string.
 14. A method, as set forth in claim 13, further comprising heating the drill string prior to injecting the elastomeric element into the void.
 15. A method, as set forth in claim 13, further comprising heating the drill string during at least a portion of the time that the elastomeric element is being injected into the void.
 16. A method, as set forth in claim 13, further comprising heating the mandrel prior to injecting the elastomeric element into the void.
 17. A method, as set forth in claim 13, further comprising heating the mandrel during at least a portion of the time that the elastomeric element is being injected into the void.
 18. A method, as set forth in claim 13, wherein injecting an elastomeric material into the void further comprises injecting a synthetic rubber into the void.
 19. A method, as set forth in claim 13, wherein injecting an elastomeric material into the void further comprises injecting a synthetic rubber copolymer into the void.
 20. A method, as set forth in claim 13, wherein injecting an elastomeric material into the void further comprises injecting a Nitrile rubber into the void.
 21. A method, as set forth in claim 13, wherein injecting an elastomeric material into the void further comprises injecting a Nitrile butadiene rubber into the void. 